1. Field of the Invention
The invention relates generally to a drawworks apparatus having a drive mechanism and a brake mechanism that are positioned externally relative to the operating area of the drawworks frame and a shaft which is isolated from wireline pull generated during operation of the drum spool.
2. Description of the Related Art
The drawworks is a type of winch used in the oil well drilling and service industry as a portion of a drilling or servicing rig to raise and/or lower items such as tools and lengths of pipe from a well bore from which oil or other hydrocarbons are produced.
The drawworks typically includes a large-diameter spool that typically supports a length of cable, one or more brakes, a drive system connecting the spool to a power source, and other auxiliary devices that may assist in the lowering and raising items into a well bore.
However, major disadvantages plague conventional drawworks designs: for instance, a major portion of the cost of manufacturing a conventional drawworks is due to the complexity of its design.
Also, a significant portion of the cost of operating a well servicing or drilling rig is maintenance. The maintenance cost is influenced greatly by the number of components requiring servicing and their accessibility.
Moreover, drumshaft failures cause the loss of braking ability in conventional drawworks and are much more likely to occur in a conventional drawworks due to the fact that it carries the line pull and must also absorb shock loads transmitted through the wire line spool.
Still another common problem with conventional drawworks is the pliability of the brake bands. The pliable nature of the brake bands is often caused by insufficient anchoring of the dead end of the brake band.
Yet and still another problem in conventional drawworks designs occurs at the brake live end, particularly, as the brake blocks wear, the brake band wraps further around the brake flange to allow the brake live end linkage to break over center and unexpectedly release the brakes.
It is still another problem with conventional drawworks designs of experiencing failure due to contamination of the clutches' frictional surfaces with oil or other foreign debris and materials. This problem is also associated with the conventional internal mounting of the brakes and other components within the drawworks frame.
An additional problem associated with conventional drawworks the use of various types of seals, usually in the form of some type of labyrinth, to prevent oil from traveling to the clutch. This is not a very reliable technique and results in many drawworks failures.
Yet and still a further problem associated with conventional drawworks apparatus is the fact that the wire line clamp is virtually hidden by the brake flange, the drawworks frame and guards, or the wear plates placed on the inside surface of the drum end.